The jet required some modification, of course. I added Milliput putty to give it a more pointed nose and to filling some gaps in the toy. I also chopped off the tail and built a thruster unit on the back where the tail would fold up on a classic Wasp. I used the jumpjet nozzles from the Wasp on the pack, but had to make the pack itself from scratch out of putty, as seen to the right. I also glued the Wasp's head to the underside of the cockpit, and later added a Missile Pod from a Warhammer 40K Tau Crisis Suit on the underside of the jet because there was too big a gap where the jet connected to the mech.
To prepare the rest of the Mech, I popped the head off and cut the torso into four chunks, the middle of which I didn't use. The other three were the upper right torso, upper left torso and waist just above the joint. I glued the torso pieces to either side of the waist and filled in the gap with Milliput, and carved a notch in the underside of the jet to fit snugly onto the nub of the waist. In this way, I preserved all of the articulation of the original figure.
From there it was just a matter of painting. I used Toffee brown as the closest match I could find to Highlander brown, and Forest Green, which is a pretty good match, plus touchup on the gunmetal and silver bits. It was only after painting that I noticed that the nozzles on the thruster pack weren't exactly aligned. Ah well.